1. Field of the Invention
This invention relates to the use of one or more coolant-to-air heat exchangers in conjunction with a cowl tray and a Heating, Ventilation, and Air Conditioning (HVAC) intake. The coolant-to-air heat exchangers are used to prevent accumulation of snow and ice, both within the intake itself, and upon the cowl tray beneath the vehicle windshield wipers. The HVAC intake may be integrated directly into the cowl tray, which cowl tray and intake may be located at the base of the vehicle windshield in a location prone to snow and ice accumulation, due to the action of the vehicle windshield wipers, and due to turbulent precipitation.
2. Description of the Related Art
Ground traveling vehicles having an occupant cabin are almost universally equipped with some form of Heating, Ventilation, and Air Conditioning (HVAC) system. This system functions to draw air from outside the occupant cabin, heat or cool it to a comfortable temperature, and introduce it into the occupant cabin. The air intake for the HVAC system may be placed at any of a number of locations external to the cabin. However, there are several advantages to locating the intake at the base of the vehicle windshield.
As a ground traveling vehicle moves, it displaces air. Relative to the frame of reference of the moving vehicle, the air flows past the vehicle. This airflow is laminar in some locations, turbulent in others, and at various angles oblique to the direction of travel depending on the geometry of the vehicle body, resulting in regions of high and low pressure. One location that exhibits consistently high pressure is at the base of the windshield, where the moving air must make a transition from the angle of the hood to the angle of windshield. This area is characterized by a region of turbulent recirculation, and somewhat elevated static pressure. For this reason, the HVAC air intake is often there located. In the same way, vehicle manufacturers have in the past located the vehicle engine air intake in the same area. Often, this was referred to as cowl induction.
An advantage to locating the HVAC air intake in a region of elevated static pressure is the fact that so doing provides greater airflow through the HVAC system and into the cabin. Even when the HVAC blower is not operating, a system having its air intake so located provides positive pressure within the vehicle cabin, thereby minimizing draft incursions and water seepage through and around the various seals and seams that are characteristic of a vehicle occupant cabin. Locating the HVAC air intake at the base of the windshield has other advantages as well. The airflow at this point is well up and away from the level at which vehicle exhaust is commonly discharged. The intake may be discreetly hidden from view by the vehicle hood. Additionally, the base of the windshield is proximate to the HVAC air distribution plenum, eliminating the need for lengthy ductwork.
There is, however, a disadvantage to having the HVAC air intake located at the base of the vehicle windshield. When moving air enters a region of turbulent recirculation, it tends to precipitate anything held in suspension. In order to deal with this effect, U.S. Pat. No. 6,868,928 teaches the use of a cowl tray, which catches and drains away moisture, although in the case of the invention taught in U.S. Pat. No. 6,868,928, the region of elevated static pressure is being utilized in an engine cowl induction system. Although the cowl tray taught in U.S. Pat. No. 6,868,928 deals well with liquid water precipitate, snow and ice accumulation at the base of the vehicle windshield continues to be a problem. The snow and ice often packs the cowl tray full, so that the windshield wipers cannot freely complete their range of motion. Snow and ice also tends to enter the HVAC intake, restricting airflow.
The situation of snow and ice entering the HVAC air intake is exacerbated by the fact that the opening of the HVAC air intake is relatively large and oriented vertically, in order to facilitate ease of routing and maximize airflow. Usually, some sort of intake screen is provided, in order to prevent leaves and other large debris from entering the HVAC system. This screen tends to be the point at which snow and ice accumulates. Further, the windshield wipers tend to push at least some snow into the area of recirculation and even directly into the HVAC air intake itself. Under certain conditions, sufficient snow and ice may accumulate to completely block the intake, reducing the amount of airflow available for heating and defrosting the vehicle windows.